The electrochemistry of platinum phthalocyanine microcrystals: I. Electrochemical behaviour in acetonitrile electrolytes

Abstract

Platinum phthalocyanine (PtPc) microcrystals deposited upon platinum, glassy carbon and gold by a process of dry abrasion have been characterised by electrochemical techniques. This mechanical abrasion can produce good electronic contact and adhesion between the microcrystals and the electrode. The redox process of PtPc microcrystals is accompanied by two reversible electrochemical phase transformations, evidenced by a sharp peak and unusually large peak potential differences. Similar to conductive polymers, an obvious first-scan discrepancy and large capacitance are observed during electrochemical oxidation. Some of the intercalated anions remain in the re-reduced microcrystals and lead to a conductivity enhancement of the microcrystals, supported by AC impedance and X-ray photoelectron spectroscopy (XPS) results. Coulometry shows that the size of the anion determines the rate and degree of oxidation, and influences the reversible phase transformations. Chronoamperometry shows diffusion-controlled nucleation and growth kinetics, controlled by the diffusion of anions into the solid films. The conformational relaxation model was used to describe this process.